Safety seat

ABSTRACT

A safety seat for a motor vehicle has a squab (1) and a back (4). A support (6) is connected to the squab and the back is pivotally connected (13) to the support (6). A motion-restricting device (22) is provided in the form of a hydraulic damper which permits relative free movement of the back of the seat rearwardly until part (12) of the back of the seat engages a stop (11), but which resists any subsequent tendency for the back of the seat to move forwardly with a pivot movement about the pivot (13) away from the stop (11).

THE PRESENT INVENTION relates to a safety seat, and in particular,relates to a safety seat intended for use in a motor vehicle, such as amotor car.

It has been appreciated that if a motor vehicle, such as a motor car, isinvolved in a rear end collision, that is to say the following vehicleruns into the back of the car, the occupants of the struck car oftensuffer from neck injuries. Such injuries are commonly called "whiplash"injuries.

It is to be understood that during the rear-end collision of this type,the vehicle that is struck is subjected to a forward acceleration. Thisimparts a forward acceleration to the seats of the vehicle. The squaband back of each occupied seat engage the posterior and torso of theoccupant of the seat and impart a substantial acceleration to theposterior and torso of the occupant. However, no correspondingacceleration is immediately imparted to the head of the occupant, as thehead is not normally in contact with the seat, or with the head-restthat may be provided on the seat. The head is a part of the body thathas substantial mass, and consequently the head has substantial inertia.

Thus, whilst the posterior and torso of the occupant of the vehicle areaccelerated forwardly as a result of the rear-end collision, the head ofthe occupant of the vehicle initially remains stationary. This may causethe neck initially to adopt an "S"-shaped configuration as the lowerpart of the neck moves forwardly, whilst remaining vertical, and theupper part of the neck remains in its initial position. Subsequently,the head begins to rotate and the neck then occupies a curvedconfiguration. The head subsequently moves forwardly. Research has shownthat "whiplash" injuries may occur when the neck changes from the"S"-shaped configuration to the cured configuration at a substantialspeed.

The present invention seeks to provide an improved vehicle seat in whichthe relative "whiplash" injuries occurring to the occupant of the seatduring a rear-end collision are reduced.

According to this invention there is provided a safety seat for use in amotor vehicle, the safety seat comprising a squab; a back associatedwith the squab, the back being pivotally connected for pivotal movementrelative to the squab, stop means being provided to limit rearwardpivotal movement of the back, a motion restricting device being providedwhich relatively freely permits movement of the back of the seatrearwardly in a pivoting motion towards said stop, but which resists anysubsequent tendency for the back of the seat to move forwardly with apivotal motion away from the stop.

Preferably the motion restricting device comprises a hydraulic cylinderassociated with a piston, the piston moving within the cylinder inresponse to movement of the back of the seat, the cylinder beingassociated with a fluid flow path which permits flow fluid in one sensethrough a non-return valve, so that the piston can move easily in onedirection within the hydraulic cylinder, and which also permits fluidflow through a throttle, which permits the piston to move in theopposite sense in the cylinder, but against a throttling effect.

Conveniently the said back is mounted for pivot movement relative tosupport means, the said motion restricting device being adapted torestrict motion of the back relative to the support means, the supportmeans being pivotally connected to the squab to permit movement of thesupport means, and the back, relative to the squab, without the motionrestricting device being operative.

Advantageously resilient means are provided to resist the pivotalmovement of the back rearwardly relative to the support means.

Preferably energy-absorbing means are provided to absorb energy when thesupport means pivot relative to the squab of the seat.

Conveniently the energy-absorbing means comprise a yieldable elementlocated between the support means and a stop.

Advantageously when a force is applied to the seat back the seat backmay execute a first movement, moving pivotally relative to the supportmeans, against a relatively low resisting force, and a second subsequentmovement, with the support means moving pivotally relative to the squab,against a relatively high resisting force.

In order that the invention may be more readily understood, and so thatfurther features thereof may be appreciated, the invention will now bedescribed, by way of example, with reference to the accompanyingdrawings in which:

FIG. 1 is a diagrammatic side view of a seat in accordance with theinvention in an initial condition,

FIG. 2 is a view corresponding to FIG. 1 illustrating the seat in thesecond condition,

FIG. 3 is a view corresponding to FIGS. 1 and 2 illustrating the seat ina further condition, and

FIG. 4 is an enlarged view of part of the seat shown in FIG. 1.

Referring initially to FIG. 1, a safety-seat for use in a motor vehiclesuch as a motor car is illustrated. The seat comprises a squab 1 whichis mounted on a support 2 which is carried by the floor 3 of the motorvehicle. A seat-back 4 is provided which is associated with the squab 1.A head-rest 5 is provided at the top part of the back 4, in aconventional position.

The squab 1 is associated with two support plates 6 (only one of whichis shown). The support plates are mounted symmetrically on either sideof the squab. Each support plate is of generally triangular form. Aforwardly directed apex of each support plate 6 is pivotally connectedto the squab 1 for pivoting motion about a pivot axis 7.

To co-operate with the support plate illustrated (and preferably alsowith the support plate which is not illustrated), a stop 8 is provided,towards the rear of the squab 1. A yieldable element 9 is provided whichis located between the stop 8 and the rear part of the support plate 6.The yieldable element 9 may comprise an element formed of rubber or maycomprise a compression spring. Preferably, the yieldable element maycomprise a permanently deformable element, such as a thin-walledcylinder made of metal.

As will become clear from the following description, the yieldableelement provides an energy-absorbing function.

The illustrated support plate 6 (and preferably also the support platewhich is not illustrated) carries two stop elements 10,11 which arelocated respectively in front of and behind a seat back support strut12. The lower end of the support strut 12 is pivotally connected to asupport plate 6 for pivoting movement about a pivot axis 13. Theseat-back support strut 12 is securely fastened to or forms part of theframework of the back 4 of the seat. Thus, the entire back of the seatis effectively supported by or on the seat back support strut 12 and canpivot about the pivot axis 13.

A spring 14 is provided, one end of which is connected to the seat-backsupport strut 12, the other end of which is connected to the supportplate 6. The spring resists rearward pivoting motion of the back of theseat, but with a relatively low resistive force.

In alternative embodiments the spring 14 may be replaced by a resilientelement such as a rubber or elastic strap.

In the illustrated embodiment, the head-rest 5 is provided with at leastone support arm 15. Two support arms may be provided located on eitherside of the head-rest. One support arm 15 is illustrated. The supportarm is pivotally connected, by a pivot 16 to the back of the seat 4. Inthe illustrated embodiment, the pivot 16 connects with the upper end ofthe seat back support strut 12.

The support arm 15 is provided with a forwardly projecting lug 17 whichcarries a pivotal connection 18 to a link arm 19. The link arm 19extends substantially parallel with the seat back support strut 12, andthe lower end of the link arm 19 is pivotally connected, at pivot point20, to the support plate 6.

It is to be appreciated that the seat will initially have the conditionillustrated in FIG. 1. The spring 14 serves to impart a forward bias orrotation to the seat back support strut 12 about a pivot axis 13, thusbringing the seat back support strut 12 into engagement with the forwardstop 10 carried by the support plate 6.

In the event that a rear impact arises, whilst the seat is occupied,initially a forward acceleration is imparted to the squab 4 of the seatthrough the support 2. The person occupying the seat will, however, haveinertia. As the squab of the seat moves forwardly, so the torso of theoccupant of the seat will apply force to the back of the seat tending tocause the back of the seat initially to pivot rearwardly about the pivotaxis 13. The back of the seat moves pivotally against the relatively lowresisting force provided by the spring 14. Thus the back of the seatpivots in a rearward sense, against a restraining force provided by thespring 14. As can be seen from FIG. 2, the back of the seat moves to aposition in which the seat back support strut engages the rear stop 11.The back of the seat thus effects a first rearward movement.

During this first rearward movement the effect of the link arm is suchthat the head-rest 5 pivots forwardly relative to the back of the seatabout the axis defined by the pivot 16. Thus, the head-rest 5effectively moves towards the head of the occupant of the seat,minimising the rearward distance that the head of the occupant of theseat travels before it engages the head-rest.

Since further rearward pivoting motion of the back of the seat 4 aboutthe pivot axis 13 is prevented, as a consequence of engagement of theseat back support strut and the rear stop 11 carried by the supportplate 16, subsequently, the back of the seat 4 pivots, together with thesupport plate 6, about the pivot axis 7, thus causing the yieldableelement 9 to yield, the yieldable element 9 provides a relatively highresisting force which resists this second movement of the back of theseat. The seat is thus moved to the condition illustrated in FIG. 3.

It is to be appreciated that during this second movement of the back ofthe seat, because the movement is effected by a pivoting movement of thesupport plate about the pivot axis 7, there is no relative movementbetween the seat back support strut 12 and the link arm 19, meaning thatduring this second phase of movement of the back of the seat, there isno forward movement of the head-rest 5 relative to the back of the seat.

It will be understood that the back of the seat, in a rear impactsituation, executes two movements, namely a first movement against arelatively low resisting force and a second movement against a greaterresisting force.

During the first movement of the seat back the head-rest moves intocontact with the head of the occupant. During the second movement, thehead and the rest of the body move together, with no relative movementbetween the head and the rest of the body.

FIG. 4 illustrates a component present on the seat which has not beenpreviously described. FIG. 4 illustrates the support plate 6, the pivot7 and the lower part of the seat back support strut 12. The link arm 19and the pivot 20 have been omitted for the sake of clarity ofillustration.

The component illustrated in FIG. 4 comprises a motion restrictingdevice 21 which permits movement of the back of the seat rearwardly in apivoting motion about the pivot axis 13, but which restricts anysubsequent tendency for the back of the seat to move forwardly with apivotal motion about the pivot axis 13. It is to be understood that itis desired for the torso and head of the occupant of the vehicle to beaccelerated, during a rear impact, to have a forward motion which isequivalent to the forward motion of the vehicle, in as smooth anduninterrupted manner as possible. Thus, as the back of the seatexecutes, the first movement and the second movement described above,the torso and the head of the occupant of the vehicle are beingaccelerated in a forward sense. It is to be understood that if the backof the seat should show any tendency of "bouncing" when the seat backsupport strut 12 engages the rearward stop 11 carried by the supportplate 6, the occupant of the vehicle would be given a very substantialforward acceleration, which would be undesirable, since it wouldincrease the role of "whiplash" injuries arising.

Thus, as can be seen in FIG. 4, a motion restricting device 21 isprovided. The motion restricting device comprises a hydraulic cylinder22 which is connected to the support plate 6. Contained within thecylinder 22 is a piston 23 which is connected by a piston rod 24 to apivoting link 25 which is connected to the seat back support strut 12.

The hydraulic cylinder 22 is provided with two inlet/outlet ports 26,27provided respectively at the opposed ends of the cylinder, theinlet/outlet ports 26,27 being inter-connected by a parallel connectioncomprising firstly a non-return valve 28 which is adapted to permit afree flow of fluid in the direction indicated by the arrow 29 andsecondly a constriction or throttle 30.

It will be understood, from considering FIG. 4, that as the seat back 4moves rearwardly with the first movement in which the seat back supportstrut 12 moves pivotally about the pivot axis 13, the spring 14 will beextended and also the piston 23 will move towards the left within thehydraulic cylinder 22. Fluid will flow through the inlet/outlet port 27,and will readily flow through the non-return valve 28 in the directionof the arrow 29, thus re-entering the hydraulic cylinder through theinlet/outlet port 26. The piston 23 will thus move relatively freelywithin the hydraulic cylinder, without any substantial resistance tomovement of the seat back support strut 12.

However, should the seat back support strut 12 show any tendency ofbouncing forwardly, after having impacted on the rear stop 11 carried bythe support plate 6, the piston 23 will tend to move towards the rightwithin the hydraulic cylinder 22. Fluid will thus leave the hydrauliccylinder through the inlet/outlet port 26. The fluid will not be able toflow through the non-return valve 28, since the non-return valve 28 willoperate to prevent fluid flow in that sense. The fluid will, however, beable to flow through the throttle or constriction 30. This means,however, that the motion restricting device 21 will provide asubstantial hydraulic damping to any forward movement of the backsupport strut 12 of the seat. Consequently, there will be severeresistance to any forward motion of the back of the seat following theabove-described first motion of the back of the seat during any accidentsituation.

It is to be understood, however, that the seat will return to itsinitial condition, as illustrated in FIG. 1, after a period of time,since the force exerted by the spring 14 on the seat back support strut12 will tend to cause the seat back 4 to pivot forwardly relativelyslowly with a flow of hydraulic fluid through the throttle orconstriction 30.

What is claimed is:
 1. A safety seat for use in a motor vehicle, thesafety seat comprising a squab; a back associated with the squab, theback being pivotally connected for pivotal movement relative to thesquab, stop means being provided to limit rearward pivotal movement ofthe back, a motion restricting device being provided which relativelyfreely permits movement of the back of the seat rearwardly in a pivotingmotion towards said stop, in response to force applied to the back ofthe seat by the torso of the occupant of the seat as a consequence of arear impact but which resists with substantial damping the subsequenttendency for the back of the seat to move forwardly with a pivotalmotion away from the stop.
 2. A seat according to claim 1 wherein themotion restricting device comprises a hydraulic cylinder associated witha piston, the piston moving within the cylinder in response to movementof the back of the seat, the cylinder being associated with a fluid flowpath which permits flow fluid in one sense through a non-return valve,so that the piston can move easily in one direction within the hydrauliccylinder, and which also permits fluid flow through a throttle, whichpermits the piston to move in the opposite sense in the cylinder, butagainst a throttling effect.
 3. A seat according to claim 1 wherein thesaid back is mounted for pivot movement relative to support means, thesaid motion restricting device being adapted to restrict motion of theback relative to the support means, the support means being pivotallyconnected to the squab to permit movement of the support means, and theback, relative to the squab, without the motion restricting device beingoperative.
 4. A safety seat according to claim 3 wherein resilient meansare provided to resist the pivotal movement of the back rearwardlyrelative to the support means.
 5. A seat according to claim 3 whereinenergy-absorbing means are provided to absorb energy when the supportmeans pivot relative to the squab of the seat.
 6. A seat according toclaim 5 wherein the energy-absorbing means comprise a yieldable elementlocated between the support means and a stop.
 7. A seat according toclaim 3 wherein when a force is applied to the seat back the seat backmay execute a first movement, moving pivotally relative to the supportmeans, against a relatively low resisting force, and a second subsequentmovement, with the support means moving pivotally relative to the squab,against a relatively high resisting force.
 8. A seat according to claim3 wherein a head-rest is associated with the back; there being a linkagebetween the head-rest and the support means, the arrangement being suchthat the head-rest will be caused to pivot forwardly, relative to theback of the seat, when the back of the seat executes a pivoting motionrelative to the support means, but the head-rest will remain in asubstantially fixed position, relative to the back of the seat, when thesupport means, together with the back, pivot relative to the squab.
 9. Aseat according to claim 8 wherein the support means comprise at leastone support plate provided on one side of the seat, the support platebeing pivotally connected to the squab of the seat and the support platebeing pivotally connected to an element associated with the back of theseat, the support plate carrying said stop means adapted to engage saidelement to limit pivotal movement of the element relative to the supportplate both forwardly and rearwardly.
 10. A seat according to claim 8,wherein the head-rest is carried by at least one support arm, thesupport arm being associated with pivot means, the support arm beingmounted by a pivotal connection provided by said pivot means to the backof the seat and each support arm having projecting means, projectingfrom the said pivotal connection, the projecting means being associatedwith a link arm extending to the support means.